A298981 - OEIS

A298981

Numbers m such that there does not exist an integer k < m for which the initial decimal digits of k/m are m.

1, 2, 4, 5, 9, 11, 12, 13, 15, 16, 18, 19, 21, 23, 24, 25, 27, 29, 31, 32, 34, 35, 38, 39, 43, 44, 45, 46, 47, 48, 49, 51, 52, 53, 54, 55, 56, 61, 65, 68, 75, 99, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 115, 116, 117, 119, 120, 121, 123, 124, 125, 127, 128, 129, 131, 132, 133, 135, 136, 137, 138, 139

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OFFSET

1,2

COMMENTS

Inspired by A298232.

LINKS

Table of n, a(n) for n=1..75.

FORMULA

Complement of A298980.

EXAMPLE

2 is in the sequence since there is no k such that k/2 would result in a decimal number which begins with 2, i.e., 0.2000. Instead, the decimal number for odd k's begin with 0.5.

MATHEMATICA

fQ = Compile[{{n, _Integer}}, Block[{k = 1, il = IntegerLength@ n}, While[m = 10^il*k/n; While[ IntegerLength@ Floor@ m < il, m *= 10]; k < n && Floor[m] != n, k++]; k == n]]; Select[Range@140, fQ]

PROG

(PARI) is_A298981(n)=!A298982(n)

CROSSREFS

Cf. A298232, A051626, A298980, A298982.

Sequence in context: A265748 A191001 A098845 * A069001 A287181 A364732

Adjacent sequences: A298978 A298979 A298980 * A298982 A298983 A298984

KEYWORD

easy,nonn,base

AUTHOR

Eric Angelini, M. F. Hasler and Robert G. Wilson v, Jan 30 2018

STATUS

approved